[PATCH] D158510: [InstCombine] Propagate nsw flag when negating

[Nikita Popov via Phabricator via llvm-commits]

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When pushing a `sub nsw 0, %x` negation into an expression, try to preserve the `nsw` flag for the cases where this is possible. Do this by passing the flag through recursive `Negator::negate()` calls.

Proofs: https://alive2.llvm.org/ce/z/QTTc6r


https://reviews.llvm.org/D158510

Files:
  llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
  llvm/lib/Transforms/InstCombine/InstCombineInternal.h
  llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
  llvm/lib/Transforms/InstCombine/InstCombineNegator.cpp
  llvm/test/Transforms/InstCombine/abs-intrinsic.ll
  llvm/test/Transforms/InstCombine/nsw.ll

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